1. Field of the Invention
The present invention relates to systems for controlling the provision of a predetermined space on a drum surface.
2. Description of the Prior Art
Systems for providing control of the line feeding and lateral spacing of a drum, such as a conventional drum utilizable in a conventional phototypesetting system, such as the type provided with the Alphasette or the Alphatype 4p or 5p incremental phototypesetting system, manufactured by Alphatype Corp. of Skokie, Illinois and, described, by way of example in U.S. Pat. No. 2,905,068, are well known. In such an arrangement, the drum is normally keyed to a common shaft with a lateral spacing control composite disc which conventionally contains four circumferential radially spaced apart bands, with each of the bands being circumferentially divided into a plurality of transparent windows spaced apart by opaque areas which are normally and preferably equal in size to the transparent windows which are optically read by a single light source in combination with a single photocell. In such a conventional arrangement, the discs each have different available disc sizes which determines the spacing, that is the lateral movement of the drum in a given line with these disc sizes being conventionally established to provide eighteen different sizes or lateral space widths for phototype setting, such as a 91/2 disc, a 15 disc, or an 18 disc, by way of example. The appropriate disc size or set size for a given job is dependent on the type font selected for the particular image and the physical appearance desired by the photocomposer. In addition, in such prior art phototype setting systems, such as the Alphatype or Alphasette, a full disc mode and a half disc mode is conventionally provided with a full disc unit and full disc mode being defined as an opaque area plus a clear area and, in the half disc mode, the opaque area also being counted so that a half disc unit is equivalent to either an opaque area or a clear area. Thus, by way of example, a 15 disc size could be utilized to also provide equivalent spacing obtainable from a 71/2 disc by utilizing a 15 disc in the half mode. As was previously mentioned, these discs are conventionally optically read by a conventional lamp and photocell arrangement to provide information to conventional counting circuitry. In such a prior art arrangement in which each of the discs is normally provided with only two zones or bands of different sizes, 240 different distinctive discs are now presently utilized to provide all of the requisite combinations to provide the normally utilized 18 zones or bands for phototype setting. Thus, prior to initating the job, with the prior art systems, the user physically selects and mates the discs, one on top of the other, which would be required to provide all of the zones required for a given job and then mechanically selects the proper zones or bands to be optically read by position setting on a rotary switch. Such a prior art arrangement does not readily allow for flexibility or changes during the course of the job. Thus, with respect to the rotary switches, such as the type utilized to manually select line feed, as well as the above, the rotary switch bank utilized for line feed selection is normally fixed for the job and cannot be changed unless the job is halted and the switch is manually changed and, accordingly, cannot be continuously varied throughout the job, such as dynamically by means of a computer to provide a programmable line feed. Other prior art lamp-photocell drum control circuits, by way of example, are described in U.S. Pat. Nos. 2,989,904; 3,726,193; 2,736,249; 3,602,116; 3,307,459; 3,357,327; 3,464,331, 2,780,151; 3,274,909; 3,450,014; and 3,138,803. These systems, however, once again, do not provide a satisfactory flexible system in which the, by way of example, the number of optically readable discs required for drum control is minimized while the number of possible different disc or set sizes corresponding to different lateral spacing increments is maximized. These disadvantages of the prior art are overcome by the present invention.